On Wed, Jun 28, 2023 at 4:53 AM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> With the addition of support for fill_link_info to the kprobe_multi link,
> users will gain the ability to inspect it conveniently using the
> `bpftool link show`. This enhancement provides valuable information to the
> user, including the count of probed functions and their respective
> addresses. It's important to note that if the kptr_restrict setting is not
> permitted, the probed address will not be exposed, ensuring security.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
documentation nit, but otherwise LGTM
Also, looking at other patch where you introduce bpf_copy_user(),
seems like we return -ENOSPC when user-provided memory is not big
enough. So let's change E2BIG in this patch to ENOSPC?
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> include/uapi/linux/bpf.h | 5 +++++
> kernel/trace/bpf_trace.c | 37 ++++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 5 +++++
> 3 files changed, 47 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 60a9d59beeab..512ba3ba2ed3 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6439,6 +6439,11 @@ struct bpf_link_info {
> __s32 priority;
> __u32 flags;
> } netfilter;
> + struct {
> + __aligned_u64 addrs; /* in/out: addresses buffer ptr */
addrs field itself is not modified, the memory it points to is
modified, so it's not really in/out per se, it is just a pointer to
memory where kernel stores output data
> + __u32 count;
but count field itself is in/out, so please add a comment explicitly
stating this
> + __u32 flags;
> + } kprobe_multi;
> };
> } __attribute__((aligned(8)));
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 03b7f6b8e4f0..1f9f78e1992f 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -2469,6 +2469,7 @@ struct bpf_kprobe_multi_link {
> u32 cnt;
> u32 mods_cnt;
> struct module **mods;
> + u32 flags;
> };
>
> struct bpf_kprobe_multi_run_ctx {
> @@ -2558,9 +2559,44 @@ static void bpf_kprobe_multi_link_dealloc(struct bpf_link *link)
> kfree(kmulti_link);
> }
>
[...]
